Messages in this thread | | | Date | Fri, 22 Dec 2000 13:25:41 -0700 | From | "Jeff V. Merkey" <> | Subject | Re: bigphysarea support in 2.2.19 and 2.4.0 kernels |
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On Fri, Dec 22, 2000 at 08:21:37PM +0100, Andi Kleen wrote: > On Fri, Dec 22, 2000 at 11:35:30AM -0700, Jeff V. Merkey wrote: > > The real question is how to guarantee that these pages will be contiguous > > in memory. The slab allocator may also work, but I think there are size > > constraints on how much I can get in one pass. > > You cannot guarantee it after the system has left bootup stage. That's the > whole reason why bigphysarea exists. > > -Andi
I am wondering why the drivers need such a big contiguous chunk of memory. For message passing operatings, they should not. Some of the user space libraries appear to need this support. I am going through this code today attempting to determine if there's a way to reduce this requirement or map the memory differently. I am not using these cards for a ccNUMA implementation, although they have versions of these adapters that can provide this capability, but for message passing with small windows of coherence between machines with push/pull DMA-style behavior for high speed data transfers. 99.9% of the clustering stuff on Linux uses this model, so this requirement perhaps can be restructured to be a better fit for Linux.
Just having the patch in the kernel for bigphysarea support would solve this issue if it could be structured into a form Alan finds acceptable. Absent this, we need a workaround that's more tailored for the requirments for Linux apps.
Jeff
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